text: A delta ray is characterized by very fast electrons produced in quantity by alpha particles or other fast energetic charged particles knocking orbiting electrons out of atoms. Collectively, these electrons are defined as delta radiation when they have sufficient energy to ionize further atoms through subsequent interactions on their own. Delta rays appear as branches in the main track of a cloud chamber (See Figs. 1,2). These branches will appear nearer the start of the track of a heavy charged particle, where more energy is imparted to the ionized electrons.